Taxon in disguise
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In bacteriology, a taxon in disguise is a species, genus or higher unit of biological classification whose evolutionary history reveals has evolved from another unit of a similar or lower rank, making the parent unit paraphyletic.[1][2] That happens when rapid evolution makes a new species appear so radically different from the ancestral group that it is not (initially) recognised as belonging to the parent phylogenetic group, which is left as an evolutionary grade.
Hypothetical example | ||||||||||||||||||
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B is phylogenetically part of the A group but not taxonomically, so A is paraphyletic. |
While the term is from bacteriology, parallel examples are found throughout the tree of life. For example, four-footed animals have evolved from piscine ancestors but since they are not generally considered fish, they can be said to be "fish in disguise".
In many cases, the paraphyly can be resolved by reclassifying the taxon in question under the parent group. However, in bacteriology, since renaming groups may have serious consequences since by causing confusion over the identity of pathogens, it is generally avoided for some groups.